Sulfur-modified chloroprene rubbers with their superior dynamic properties have been used as common industrial materials for preparation of drive belts, conveyor belts, automobile air suspensions, antivibration rubbers, and others. These products have a problem that they show a shortened product lifetime when the temperature of use environment is raised. Thus, there exists a need for development of a sulfur-modified chloroprene rubber improved in heat resistance.
Known methods for improving the heat resistance of such a sulfur-modified chloroprene rubber include, for example, a method of plasticizing (peptizing) a sulfur-modified chloroprene rubber in the presence of a special tetraalkylthiuram disulfide (see Patent Document 1) and a method of adding an unsubstituted or substituted thiazolidine-thione-2 and an imidazole group-containing compound (see Patent Document 2).